1. Field of the Invention
The present invention relates generally to a semiconductor device and, more particularly, to a semiconductor device having improved metal line structure and a manufacturing method therefor.
2. Description of the Related Art
As semiconductor devices, particularly logic devices, have become more highly integrated and operate at higher speeds, the design rule has decreased to 0.25 microns or less. Accordingly, the width of metal lines and the spacing or interval between metal lines on the semiconductor devices have become narrower. However, with a decrease in the width of the metal line, the resistance of the metal line increases, and with a reduction in the spacing or interval between metal lines, the parasitic capacitance between the metal lines increases. Such an increase in resistance or parasitic capacitance can significantly reduce the speed of a semiconductor device, especially in a logic device.
In order to suppress an increase in capacitance between the metal lines, a dielectric material having a low dielectric constant k is required to be used as an interlayered dielectric material or an intermetallic dielectric material. There are two basic types of dielectric materials having a low dielectric constant k: an organic material and an inorganic material. Silicon oxyfluoride (SiOF) is an example of an inorganic material that exhibits a low dielectric constant. This material may be formed by a high density plasma process or other processes.
FIGS. 1 and 2 are cross-sectional views for illustrating the problems and shortcomings of a conventional metal line structure.
Referring to FIG. 1, when a SiOF film is used as a dielectric film 40 covering an anti-reflection layer 35 and a metal film pattern 31 formed on a dielectric layer 20 and a semiconductor substrate 10, the metal film pattern 31 is subject to attack by a harmful or reactive material, such as fluorine, contained in the dielectric film 40, resulting in the generation of a damage film 37. More specifically, a harmful material or reactive material, such as fluorine, diffuses to the metal film pattern 31 and reacts with metal elements in the metal film pattern 31 to form the damage film 37. As a product of such a reaction, the damage film 37 is formed of a metal fluoride, a highly resistive material. The formation of the damage film 37 may therefore cause an increase in the resistance of the metal film pattern 31, thereby degrading the reliability of the metal line and causing a failure of the semiconductor device.
Meanwhile, damage to the metal film pattern 31 as described above may also occur in a metal line fabrication process including a process for forming a via contact plug, etc. Referring to FIG. 2, when an upper metal film 55 to be connected to a lower metal film pattern 31 is formed, the lower metal film pattern 31 may be damaged by a source gas which is used to form the upper metal film 55 or by a reactive material produced by the source gas, thereby producing a damage film 39 on the lower metal film pattern 31.
For example, when the upper metal film 55 is a tungsten film, the tungsten film is formed from a reactive gas including source gases such as tungsten hexafluoride (WF6). A contact hole exposing the lower metal film pattern 31 is formed by selectively etching the first and second dielectric films 40 and 45. Since semiconductor devices are highly integrated, it is difficult to accurately align the contact holes with respect to the lower metal film pattern 31 when the contact holes are formed. In particular, when via contact holes are formed in a logic device, misalignment may occur due to a very small edge portion. Accordingly, a sidewall surface of the lower metal film pattern 31 is generally exposed together with the upper surface of the lower metal film pattern 31.
The upper portion of the lower metal film pattern 31 and the bottom surface of the contact hole form a recess (A) because of the misalignment. Because the recess (A) has a significant high aspect ratio, the step coverage of a glue layer 51 is weakened. This degradation in the step coverage may generate a step coverage failure so that the sidewall surface of the lower metal film pattern 31 may be exposed.
The exposed sidewall surface of the lower metal film pattern 31 contacts a source gas such as a tungsten hexafluoride gas introduced when the upper metal film 55 is formed, or a reactive material such as fluorine produced by the source gas. The reactive material, e.g., fluorine, is diffused into the lower metal film pattern 31, and reacts with the metal of the lower metal film pattern 31, thus forming a highly resistive material 39 such as a metal fluoride. Therefore, a resistance failure may occur in which the resistance of the lower metal film increases or the contact resistance between the upper metal film 55 and the lower metal film pattern 31 increases, resulting in a failure of the semiconductor device.
The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set forth above.
In accordance with one aspect of the present invention, there is provided a semiconductor device comprising a first dielectric layer formed on a semiconductor substrate, a metal film pattern formed on the first dielectric layer, an interface protection layer formed on the metal film pattern, and a second dielectric layer formed on the interface protection layer. The interface protection layer may be formed of aluminum oxide, silicon nitride or silicon oxynitride and prevents any reactive material in the second dielectric layer from diffusing to and attacking or reacting with the metal film pattern, especially when the reactive material is fluorine as may be the case when the second dielectric layer is formed of silicon oxyfluoride (SiOF).
In accordance with another aspect of the present invention, there is provided a semiconductor device comprising a first dielectric layer formed on a semiconductor substrate, a first metal film pattern formed on the first dielectric layer, an interface protection layer formed on the first metal film pattern, a second dielectric layer formed on the interface protection layer, a contact hole extending through the second dielectric layer and the interface protection layer to the first metal film pattern, a protection spacer covering the side walls of the contact hole, an adhesion layer formed on the second dielectric layer and along the side walls and bottom walls of the contact hole, and a second metal layer formed on the adhesion layer and extending into the contact hole.
The second dielectric layer is a dielectric layer, e.g., a silicon oxyfluoride layer, containing a reactive material, such as fluorine. The adhesion layer is formed on the exposed first metal film pattern and may be a double layer formed by stacking a titanium layer and a titanium nitride layer.
The interface protection layer may be formed of aluminum oxide, silicon nitride or silicon oxynitride and prevents any reactive material in the second dielectric layer from diffusing to and attacking or reacting with the metal film pattern, especially when the reactive material is fluorine as may be the case when the second dielectric layer is formed of silicon oxyfluoride (SiOF). It is preferable that the interface protection layer be formed of aluminum oxide.
In accordance with yet another aspect of the present invention, there is provided a method of manufacturing a metal line structure for semiconductor devices, by which the resistance of a metal film pattern can be prevented from increasing by protecting the metal film pattern from damage due to harmful or reactive material contained in a dielectric film.
In accordance with still another aspect of the present invention, there is provided a method of manufacturing a metal line structure for semiconductor devices, by which the contact resistance between a lower metal film pattern and an upper metal film can be prevented from increasing by protecting the lower metal film pattern from damage due to a reactive material contained in a source gas which is used to form the upper metal film to contact the lower metal film pattern.
In the method of manufacturing a metal line structure for a semiconductor device, first, a metal film pattern is formed on the first dielectric layer on a semiconductor substrate. A second dielectric layer for insulating the metal film pattern is formed. The second dielectric layer is an insulative layer, e.g., a silicon oxyfluoride (SiOF) layer, containing a reactive material, such as fluorine, which reacts with the metal film pattern. The silicon oxyfluoride is formed by high density plasma chemical vapor deposition.
An interface protection layer is formed at the interface between the second dielectric layer and the metal film pattern, to protect the metal film pattern by preventing the reactive material, e.g., fluorine, from being diffused from the second dielectric layer to the metal film pattern. The interface protection layer is formed of a material selected from the group consisting of aluminum oxide, silicon nitride, and silicon oxynitride, to cover the metal film pattern. Preferably, the interface protection layer is formed of aluminum oxide.
The interface protection layer may be formed by sequentially depositing multiple aluminum oxide sublayers. For example, the aluminum oxide interface protection layer is formed by atomic layer deposition. If a silicon nitride layer or the silicon oxynitride layer is used, then it may be formed by chemical vapor deposition or plasma deposition.
In still another aspect of the present invention, there is provided a method of manufacturing a semiconductor device having an improved line structure, wherein a first metal film pattern is formed on a first dielectric layer on a semiconductor substrate. A second dielectric layer having a contact hole exposing the first metal film pattern is formed to insulate the first metal film pattern. The second dielectric layer is formed of a dielectric material, e.g., silicon oxyfluoride (SiOF), containing a reactive material, such as fluorine, which reacts on the first metal film pattern. The silicon oxyfluoride is formed by high density plasma chemical vapor deposition.
An interface protection layer is formed at the interface between the second dielectric layer and the metal film pattern, to protect the metal film pattern by preventing the reactive material, e.g., fluorine, from being diffused from the second dielectric layer to the first metal film pattern. The interface protection layer is a layer selected from the group consisting of aluminum oxide, silicon nitride, and silicon oxynitride, covering the first metal film pattern. Preferably, the aluminum oxide layer is used as the interface protection layer.
The interface protection layer may be formed by sequentially depositing multiple aluminum oxide sublayers. If a silicon nitride layer or silicon oxynitride layer is used, then it may be formed by chemical vapor deposition or plasma deposition.
A protection spacer is formed of a material selected from the group consisting of aluminum oxide, silicon nitride, and silicon oxynitride within the contact hole, to protect the exposed first metal film pattern by covering the sidewall of the contact hole and the sidewall of the exposed first metal film pattern while exposing the upper surface of the first metal film pattern.
The step of forming the protection spacer includes the steps of forming a protection layer for covering the first metal film pattern, in the contact hole, and exposing the upper surface of the first metal film pattern by anisotropically etching the protection layer. The anisotropic etching is performed by an inductively coupled plasma method or RF sputtering method.
The interface protection layer may be formed by sequentially depositing multiple aluminum oxide sublayers. For example, the interface protection layer is formed by atomic layer deposition. Also, the silicon nitride layer or silicon oxynitride layer is formed by chemical vapor deposition or plasma deposition.
A contact layer is formed on the exposed first metal film pattern in the contact hole. The contact layer prefeerably comprises an adhesion layer and a second metal layer. The adhesion layer preferably comprises a double layer formed by stacking a titanium layer and a titanium nitride layer.
A second metal layer for filling the contact hole is formed using a tungsten layer on the adhesion layer. The tungsten layer is formed using a gas, such as tungsten hexafluoride gas, containing a reactive material, e.g., fluorine, which reacts on the first metal film pattern. Here, the protection spacer protects the first metal film pattern from the reactive material, e.g., fluorine.
According to the present invention, a metal film pattern to be used as a interconnection line can be protected from damage due to movement of a harmful or reaction material contained in a dielectric film. Also, the lower portion of the metal film pattern can be protected from damage due to diffusion or other movements of a reactive material contained in a source gas which is used when another metal film to contact the metal film pattern is formed. Therefore, the resistance of the metal film pattern can be prevented from increasing, and likewise for the contact resistance between the metal film pattern and another upper metal film.